1. Technical Field
This invention relates to a cutting blade for a rotary lawn mower wherein the elongated blade rotates about a vertical axis at a midpoint of its longitudinal and transverse dimensions.
2. Prior Art
A wide variety of cutting blades have been suggested for rotary mowers. In nonmulching mowers, blades have been designed to sever the grass and to aid in discharging the cut grass through a discharge opening in the blade housing or through a chute to a side or rear mounted catcher. Heretofore, others have provided upwardly angled lift portions at the outer ends of the blade to lift the grass clippings and provide air movement to carry the air entrained grass clippings to the discharge portion of the mower blade housing. Prior art patent U.S. Pat. No. 2,836,029 shows a blade made from a generally rectangular shaped blank with cutting edges at the leading portions near the radially outer ends of the blade and inclined lift portions in trailing relation to the cutting edges. In U.S. Pat. No. 3,315,451 a rotary blade is shown and described as having cutting edges which, along their lengths, extend obliquely radially outwardly and rearwardly relative to the direction of blade rotation, thus increasing the radially outward force exerted on the grass during a cutting operation. The blank from which the blade of U.S. Pat. No. 3,315,451 is formed is eight sided in its top view and thus it is more expensive to form as compared to a parallelogram shaped blade blank. In this last mentioned patent disclosure, it will also be noted that the edges at the opposite ends of the blade extend at right angles to the longitudinal axis of the blade and the lift portions are bent upwardly along lines parallel to the longitudinal axis of the blade. This results in the radially outer tips of the cutting edges lying a substantial distance inwardly from the circle generated by the radially outer trailing tip of the lift portions of the blade. In using this prior art mower, a substantial width of the outer tip of the lift portions is forced through grass not severed by the leading cutting edge.